Multi-circuit power distribution systems for modular wall panel units are disclosed in U.S. Pat. No(s). 4,367,370, issued Jan. 4, 1983; 4,740,167, issued Apr. 26, 1988 and 4,781,609, issued Nov. 1, 1988. Each of these systems include "power blocks", also termed "junction boxes" into which a duplex outlet may be plugged in one or both of its opposite faces. The power blocks of the systems of the referenced patents carry multiple circuits and the duplex outlets used in the systems employ various means for selecting a particular circuit, from amongst the several circuits available in a power block, to which that duplex outlet is to be connected.
For example, the systems of Pat. No(s). 4,367,370 and 4,740,167 receive power from a three phase, shared neutral, base power distribution system. The panel distribution systems each carry three line conductors and one neutral conductor. The duplex outlet units are connected between a selected one of the lines and neutral.
The duplex outlet unit used in the system of Pat. No. 4,367,370 has four male prongs which plug into the power block to contact individually the neutral and three line conductors therein. The outlet unit has an internal switch by which the line contacts, i.e., the outlet contacts for one side of an external load circuit, are connected to a selected one of the phases. Since all outlet units of the system are connected to the same neutral line, switching of the outlet contacts for the neutral side of an external load circuit is not required.
The system of Pat. No. 4,740,167 uses three different types of outlet units to connect the outlet units to the three separate lines of the system. The outlet units are basically the same and all use the same form of outlet housing and have male prongs for connecting the load circuit and load safety ground contacts of the outlet to the line, neutral and safety ground conductors of the system. The three types of outlet units differ from one another only in the placement of the outlet line prong so as to engage a different one of the three line contacts in the system power block, and in the configuration of the conductive strip that links the line prong of the outlet to the outlet contacts for the line side of an external load.
The system of U.S. Pat. No. 4,781,609 carries three separate pairs of line and neutral conductors to eliminate the sharing of a single neutral conductor by the loads connected to the three separate lines, as is done in the systems of the '370 and 167 patents. The outlet units used in the '609 system have a pair of contact prongs for engaging a selected pair of the three separate pairs of line and neutral conductors carried by the power block of the system. The outlet line and neutral prongs are slidably mounted in vertical alignment on the outlet unit to allow those prongs to be set in a position to engage a selected pair of line and neutral contacts from among the three vertically aligned pairs of line and neutral contacts on the power block.
It is an object of the invention to provide an outlet unit for use in a power distribution for modular furniture units and which may be selectively connected to a particular pair of line and neutral conductors from amongst the multiple pairs of line and neutral conductors carried by the panel power distribution system.
It is another object of the invention to provide a duplex outlet unit for use in such a power distribution system and which possesses increased reliability due to the elimination of slidable contacts therein for line and neutral pair selection.
It is a further and more specific object of the invention to provide a outlet unit for use in a power distribution system having four separate pairs of line and neutral conductors, which outlet unit may be connected to a selected pair of two of the available pairs of line and neutral conductors of the system and, by a simple modification of the outlet unit, may be connected to a selected pair of the remaining pairs of line and neutral conductors of the system.